Method for coating paper



p l938- J. D. MacLAURIN 2,130,241

I I METHOD FOR COATING PAPER Filed June 18, 1934 2 Sheets-Sheet 1 I a wSept. 13, 1938. J. DVM LAURIN 2,130,241

METHOD FOR COATING PAPER Y Filed June 18, 1934 i 2 Sheets-Sheet 2 avzes$12100! a are)? Patented Sept. 13, 1938 UNITED STATES METHOD FOR COATINGPAPER;

James D. MacLaurln,

East Orange, N. J., as-

slgnor to Seaman Paper Company, Chicago, Ill., a corporation of IllinoisApplication June 18, 1934, Serial No. 731,028

- 1 Claim.

This invention relates to improvements in a method and means for coatingpaper to render the same suitable for printing purposes, and refersspecifically to a method and means for smoothing and uniformlycompacting a mobile coating material or materials upon a paper web whichhas been previously applied to said web in a rough or uneven state.

The objects and advantages of my invention will be apparent from theaccompanying drawings and following detail description.

In the drawings, Fig. 1 is a diagrammatic side elevational view ofsuitable apparatus for carrying out my invention.

Fig. 2 is a diagrammatic plan view of the apparatus of Fig. 1.

Fig. 3 is a diagrammatic side elevational view of the air knife used inspreading and smoothing the coating material or color.

Fig. 4 is a diagrammatic side elevational view of the coating materialor color application means.

Referring in detail to the drawings, I indicates a platform or tablesupported by uprights 2. A

roll 3 of flexible material such as paper or the like may be mountedupon supports 4 and a web 5 may be led therefrom over the upper surfaceof platform I. It is to be understood that web 5 is intended torepresent any type of flexible web and platform I and the operationsperformed upon said platform, to be hereinafter described, may beutilized in conjunction with a paper mak-- ing machine, in which caseweb 5 will comprise the newly formed web passing from the paper machinebefore, after or during passage through the driers.

Web 5 may be carried over platform I in a continuous manner and in sotraveling, passes beneath color spray pipe 6. Pipe 6 is provided with aplurality of spaced apertures I from which coating material or color isdischarged.

A pump 8 may be mounted upon foundation 9 beneath platform I and may bedriven by motor In mounted upon foundation I I. Pipe I2 may be connectedto the intake side of pump 8, said pipe being connected at its oppositeend to a source of supply of color (not shown). The discharge of pump 8may be connected to pipe I3 which may be joined by elbow I4 to pipe I5.A shut-off valve I6 and pressure control valve I] may be interposed inpipe I5. The end of pipe I5 may be joined by means of elbow I8 to pipeI9 which may be connected with T 20. One arm of T 20 may be connected topipe 2| and a pressure gauge 22 may be connected in said latter pipe formeasuring the. color pressure. A shut-off valve 23 may be interposed inpipe 2| and may be adapted to control the flow of color in said pipe.The opposite end of pipe 2| may be joined by means of elbow 24 to pipe25 which may, in turn, connect into one end of spray pipe 6. By thisarrangement, color in desired quantities and at suitable pressure may bedelivered to pipe 6. The opposite end of spray pipe 6 may be connectedby means of pipes 26, 21 and 28 to pipe I2 and is adapted to serve as ameans for returning excess color from spray pipe 6 to the intake of pump8.

An air pipe 29 may be positioned above color spray pipe 6 andmay carry aseries of spaced 1 nozzles 30 which may register with apertures I inpipe 6. Pipe 29 is adapted to carry air or other fluid under pressureand nozzles 30 may be so positioned as to cause the streams of airissuing from said nozzles to impinge upon the sprays of color issuingfrom apertures I. In this manner the color is sprayed upon the uppersurface of the web 5 in the form of a finely divided mist, the airstreams acting to break up the streams of color into finely dividedparticles and spreading the same over the entire surface of the web in amanner more or less uniform and regular.

The air or other fluid adapted to be discharged from the pipe 29. may bepassed to the system from a source of supply (not shown) through pipe31, the air or fluid being under superatmospheric pressure. Pipe 3| maybe connected by means of T coupling 32 to pipe 33 which in turn maybe.connected into a conventional pressure reducer 34 wherein thepressure may be reduced before application, said pressure depending uponvarious factors including the web speed, color pressure, characteristicsof the color and thickness of coating desired. After passing throughreducer 34 the air orfluid is passed through pipe 35 which is joined topipe 36 by means of T 31. Pipe 36 is in turn connected by means of elbow38 to the pipe 39 which connects into pipe 29, pipe 36 havinginterconnected therein a control valve 40.

The pressure of the fluid discharged from pipe 29 varies in accordancewith the coatings used and the amount of coating material to be appliedto the web. I preferably control the coating applied so that all of saidcoating material remains upon the web and little or none is blown off aswill be hereinafter described. When usingbcoating of relatively lightconsistency, the fluid pressure may be reduced and conversely if thecoating material is heavy the fluid pressure is insprayed color and theweb is more or less loose,.

the color being susceptible of being readily lifted from the web.Consequently, the function of the air knife is to smooth and evenlyspread the color upon the web and compact or incorporate the color intothe surface pores of the web so.

that a smooth surface capable of receiving print may be obtained.

The air knife may be constructed in many forms, but for purposes ofillustration and description, the air knife will be exemplified by thefollowing construction. The air knife may comprise a cylinder 42 beingclosed at both ends by caps 43. An elongated slit 44 may be provided incylinder 42 which may extend throughout a substantial portion of thelength of the cylinder. The slit 44 may be defined by flanges 45,creating what may be referred to as a narrow elongated nozzle.

In operation, air or other desired fluid under pressure may beintroduced into each end of the cylinder 42 through openings 45 providedin caps 43. The fluid thus introduced will be described through slit 44and by means of flanges 45 will be directed in the form of an elongatedwall of fluid. Flanges 45 may be aimed or directed at the surface of webpassing therebeneath, the wall of fluid impinging upon the color uponsaid web at right angles as shown or at any other desired angle.

Air or fluid under pressure for the air knife 4| may be derived from anydesired source of fluid pressure, or, as shown, the fluid may be derivedfrom the same source that supplied pipe 29. In this latter case, a pipe41 may connect at one end into T 32, the opposite end of said pipe beingjoined to pipe 48 by means ofelbow 49. Pipe 48, in turn, may beconnected to pipe 5|) by means of elbow 5| and a control valve 52 may beinterposed in said latter pipe. The end of pipe 50 may be joined byelbow 53 to nipple 54 to the Y-connection 55, each arm of which lattermay be connected to flexible conduit 55 which, in turn, connects intoopenings 46 in caps 43.

It can readily be seen that the fluid pressure applied to air knife 4|may be the same as that at the source to which pipe II is connected, orthe same may be reduced by valve 52. If desired, the fluid may bederived from an independent source of pressure. In addition, it isdesirable that the pressure of the fluid discharged from slit 44 beuniform throughout thelength of the slit and therefore the volume ofcylinder 42 may be relatively great with respect to the area of slit 44.

As has beenv hereinbefore described, when the color is initially appliedto web,5 it is applied uniformly on the surface of the web but ifpermitted to dry in this conditon the surface would not be smooth oreven enough for printing or like purposes. Consequently, while the coloris still in a mobile state upon the web surface, the fllm of color issubject to the impingement of the wall of air or other fluid dischargedfrom slit 44 at high velocity. The fluid thus discharged smooths thecolor film and compacts the color upon the web and forces the solidparticles of the color into the pores of the web. In addition, aconsiderable portion of the moisture in the coating or color isevaporated facilitating the drying of the coating. The rapid drying thusobtained permits paper to be coated in conjunction with the fastestrunning paper making machines, as the coated surface would besufficiently dry to come in contact with felts or hot driers (not shown)without sticking to either, or damaging the surface of the coating insuch contact. In this connection, if desired, the fluid discharged fromthe air knife may be preheated by passing the same overelectric heatingcoils (not shown).

In view of the fact that the air or other fluid discharged from the airknife 4| is discharged at relatively high velocity, splashing mayoccurwhen the wall of fluid impacts with the film upon the web depending uponthe degree of mobility of the fllm upon the web. Hence, in order toprevent undue splashing and spatterlng I provide a continuously rotatingdrum 5'! which is adapted to catch the drops of color splashed from theweb. Drum 51 may be mounted upon shaft 58 supported by standards 59 andsaid shaft may be rotated in the direction shown by the arrow by pulley60 which may be driven by belt 6|.

A scraper 52 may bear upon the surface of drum 51 and may collect all ofthe coating material splashed upon the drum. A vacuum pipe 83 having anelongated nozzle 64 may be positioned adjacent scraper 62 and may suckup and remove the coating material accumulated. Pipe 63 may be connectedto any suitable source of vacuum (not shown).

The surface of drum 51 may be constructed of brass or copper and ispreferably highly polished or, if desired, it may be covered with rubbersheeting. If desired, the vacuum pipe 53 may be eliminated, in whichevent, the coating material accumulated by scraper 52 may be run off toa scupper (not shown) and from there back to the color supply, thussaving all loss of color as well as preventing dirt and excess coloraccumulating on the machine.

If desired, other means may be used for catching the splashed color, forinstance, a continuously traveling blanket may be disposed adjacent airknife 4| in place of drum 51 and vacuum means similar to pipe 53 may beused to remove the color collected by said blanket in the same mannerthat pipe 53 collects the color from drum 51.

Web 5 after passing beneath air knife 4|, if desired, may be dried, theresulting sheet even with one application of'coatlng being suitable forcertain types of printing. However, said web before described and theparts thereof will be designated by primed numerals referring tocorresponding parts of the flrst unit.

Pipe 5 may be connected to the color supply' system by means of pipe 25'which may be joined to pipe 2| by means of elbow 24'. A valve 23' vmaybe interposed in pipe 2| and may serve to control the passage of colorthrough said pipe.

The opposite end of pipe 5 may be connected by means of pipe 26' to thecolor return pipe 21, Pipe 29' may be connected by means of pipe 39',elbow 38' to pipe 36' which latter connects into T 31. A valve 40' maybe interposed in pipe 36' and controls the passage of air or other fluidto pipe 29'. The ends of air knife 4| may be connected by means of theflexible conduits 56' to the Y-connection 55' which, in turn, isconnected by nipple 54 to pipe 50, a valve 52' being interposed in saidnipple whereby air knife 4| may be controlled independently of air knife4|.

As a feature of my invention, the weight of coating applied to the papercan be closely con-' trolled by varying the web speed, the colorpressure, the velocity of the fluid issuing from the air knife, or theconsistency or fluidity of the color. Moreover, it is contemplated thatsubstantially all of the color initially applied to the web will remainthereon and will not be removed or blown off by the air knife.

In the case of relatively high web speeds, high fluid velocity from theair knife, high color pressure without correspondingly increased webspeed, or variable fluid pressure at the air knife, the color may tendto accumulate upon local portions of the web, usually in front of theair knife. To prevent this non-uniform local accumulation, a vacuum pipe12 having openings (not shown) facing the web, may be positionedadjacent and transverse with respect to the web immediately in front ofthe air knife. This vacuum pipe tends to suck up and remove excess colorwhich may accumulate in front of the air knife and consequently auniform coating is insured. The vacuum pipe 12 may be positioned adistance above the passing web such as to normally not interfere withthe color upon the web. However, when an excess of color is built up infront of the air knife, this color must be disposed of and in order toprevent the same being forced oi the web at the sides, the vacuum pipe12 is provided.

It is to be understood that the coating material may be initiallyapplied to the web in any desired manner, such as, by means of rolls,brushes, stationary or rotating sprays, or by dipping the web in a bathof coating material. In addition, one or both surfaces of the web may becoated and as many coating units as desired may be used in series.

If desired, the first coating unit may apply a relatively cheap coatingsubstance, such as china clay, for instance, while the second coatingunit may apply a more expensive coating such as blanc flxe, forinstance. In this manner a fine finished paper may be produced atrelatively low cost. In most coating systems heretofore used the twocolor materials are mixed and put on at one time on the coating machine,a larger proportion of expensive coating, say about 75% to 25% of cheapcoating is necessary, while, on the other hand, in my process the bodyof the coated paper'is built up and the pores thereof are filled with acheap coating and the flnal coating is of a relatively small proportionof expensive material. By this method bulk is gained, a very essentialfactor in paper coating.

It is to be understood, of course, if two different type color materialsare used, a separate pump will be provided for each coating unit. Inaddition, as many of the same or different coatings may be applied asdesired, with corresponding obvious changes in equipment.

My process of coatingis particularly adaptable for use with a papermaking machine inasmuch as eflicient coating may be obtained atrelatively high web speeds corresponding to those of the usual papermaking machines. Moreover, the coating operation may take place whilethe web is still relatively wet and yet a smooth, uniform coating willbe obtained which will not be lifted from the web when the same'iscalendered.

If desired, the web may be coated while traveling in a vertical orinclined direction, in which case, however, an excess of coatingmaterial is initially deposited since the air knife will blow some ofthe mobile coating material from the surface of the web.

In view of the fact that the coating as applied by my process setsrelatively quickly, the opposite side of the web may be coated in themanner described, the coating of both faces of the web being carried outas a continuous operation without rewinding the web and passing itthrough the coater a second time for the purpose of coating the oppositeside.

By the term compacting as used in the specification and claim, is meantthat action of the fluid or air under pressure travelling at highvelocity which forces or pounds the coating material into the pores andirregularities characteristic of the surface of paper, and also theaction which densities the coating material upon the surface of thepaper.

I claim as my invention:

A method of coating paper for printing pur-,

thereon.

JAMES D. MACLAURIN.

